Date: Wed, 12 Dec 2001 15:09:28 +0100 From: Bernd Walter <ticso@cicely8.cicely.de> To: Terry Lambert <tlambert2@mindspring.com> Cc: Warner Losh <imp@harmony.village.org>, Danny Braniss <danny@cs.huji.ac.il>, Mike Smith <msmith@FreeBSD.ORG>, freebsd-hackers@FreeBSD.ORG Subject: Re: irq Message-ID: <20011212150928.F15654@cicely8.cicely.de> In-Reply-To: <3C17393B.8297E824@mindspring.com> References: <3C1614D5.B5C3B4C5@mindspring.com> <E16Dk3D-000AIb-00@pampa.cs.huji.ac.il> <200112120516.fBC5GJM33101@harmony.village.org> <3C17393B.8297E824@mindspring.com>
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On Wed, Dec 12, 2001 at 03:02:19AM -0800, Terry Lambert wrote: > How is setting a local register when an interrupt is triggered > antithetical to such cards working? I know of several network > cards where I've personally hacked on the driver that have such > a register. > > It's not possbile to take a shared interrupt and not run the ISR, > but it's possible for the ISR to check the register and decide on > that basis, rather than on data availability, that it will or will > not do work. > > I think that everyone now "gets" that PCI interrupts are like > signals, in that they are persistant conditions, so more than one > card asserting them doesn't change the fact that "an interrupt" > was asserted, and there's no way to tell _from the interrupt_ > which cards did or did not assert it in the first place. But we > are talking about an extra hardware register on the card that the > card sets when it asserts an interrupt, so an ISR can look to ask > the card "did you assert an interrupt?" and decide not to process > if the answer is "no". > > The Tigon II interrupt sharing in fact depends on this, or when > you had two Tigon II cards, you migh spend the rest of eternity in > the ISR. I never understood why the PCI-bus is not a interupt vector design. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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